Hydraulic shock-absorbing device

ABSTRACT

A hydraulic shock-absorber of the oleo type with a double-acting piston and cylinder containing a damping fluid has an outer casing around the cylinder with an annular space interposed therebetween and communicating at its ends to the ends of the cylinder to constitute a fluid storage chamber, and this chamber is communicatively connected to a cooling device for cooling the fluid in the chamber and the cylinder, the fluid in the cylinder being caused by the movements of the piston to flow through the chamber and in and out of the cooling device.

i United States Patent 1 1 Naito et a1.

1541 HYDRAULIC SHOCK-ABSORBING DEVICE [75] Inventors: Masaharu Naito,Hamamatsu;

Masae Watanabe, Iwata, both of Japan [73] Assignee: Yamaha HatsudokiKabushiki Kaisha, Iwata-shi, Japan 22 Filed: Sept. 18,1972

21 Appl. No.: 289,943

30 Foreign Application Priority Data Sept. 17, 1971 Japan 46-71770 [52]US. Cl. 188/274, 188/315 15 1 v :1111. F161? 9/42 [58] FieldofSearch188/ 274,314,315,264 D,

so References emu 'UNITEDSTATES PATENTS 2,410,539 11/1946 Whisler, Jr188/314 3,701,402 10 1972 Chelnokov m 188/314 Mar. 5, 1974 FOREIGNPATENTS OR APPLICATIONS 6 8 ,45 o 6/1958 Belgium 188/274 955,537 6/1949France 1 188/315 1,123,417 6/1956 France 1 1 188/314 1,144,380 4/1957France 188/274 767,756 2/1957 Great Britain... 188/274 536,828 12/1955Italy .1 188/315 Primary ExaminerGeorge E. A. Halvosa I Attorney, Agent,or Firm-Holman & Stern [57] ABSTRACT A hydraulic shock-absorber of theoleo type with a double-acting piston and cylinder containing a dampingfluidhas an outer casing around the cylinder with .aaamular spac e p iie sbqt nd municating at its ends to the ends of the cylinder toconstitute a fluid storage chamber, andthis chamber is communicativelyconnected to a cooling device for cooling the fluid in the chamber andthe cylinder, the fluid in the cylinder being caused by the movements ofthe piston to flow through the chamber and in and out of thecoolingdevice.

7 Claims, 5 Drawing Figures PATENTEB MAR 5 I974 SHEET 2 0f 5 PATENTED 5E74 SHEET 3 BF 5 FIG.3

PATENTEDHAR 5!.974

sum 5 or 5 weather.

1 HYDRAULIC SHOCK-ABSORBING DEVICE BACKGROUND DRAWINGS In the drawings:FIG. 1 is a fragmentary side view showing one exam- This inventionrelates generally to shock-absorbing 5 ple of the hydraulic shockabsorbing device according devices and more particularly to'a new andadvanced hydraulic shock-absorbing device for use in vehicles,especially motor vehicles such as motorcycles.

When motor vehicles are being driven on paved roads, the hydraulic oroleo shock absorbers or shock dampers thereof undergo almost noup-and-down motion relative to the vehicle chassis, butwhen the vehicleis running over uneven ground such as rough terrain, the hydraulicshock-absorbers undergo rapid extension and constraction movements.

In general, a hydraulic shock-absorber of the instant charactercomprises, essentially, a cylinder filled with a damping fluid such asan oil and a piston slidably fitted in the cylinder and having smallholes and check valves, through which the fluid flows when the pistonslides within'the cylinder, whereby oscillatory reciprocative movementsoccurring mutually between the piston and the cylinder are damped.Accordingly, when the vehicle rides over rough terrain, the up-and-downmovements of the piston are vigorously repeated,.and the temperature ofthe internally contained fluid rises rapidly. Consequently, theviscosity of the fluid de creases to a very low value, whereby thedamping effect with respect to the 'recipro c'ative movement becomesvery small or nonexistent. This gives rise to a loss of stability of thevehicle and a drop in its drivability. This difficulty tendsto occurfrequently particularly in hot SUMMARY It is an object of this inventionto provide a hydraulic shock-absorbing device in which rise oftemperature of the damping fluid contained within the cylinder issuppressed to minimize lowering of the fluid viscosity, and impairmentof the damping characteristic of the device as a shock-absorbing deviceis prevented.

According to this invention, briefly summarized, there is provided ahydraulic check-absorbing device for use in vehicles having a hydrauliccylinder containing a damping fluid and receiving therein in a pistonwhich divides the cylinder interior into upper and lower chambers and isconnected, to a piston rodfor transmission of externalaxial forces tothe piston said shock- 'ab sorbing device further comprising a dampingfluid cooling device provided at the lower part of the cylinder, and avehicle weight carrying suspension coil spring disposed around thecylinder substantially above the cooling device. I

It is also an object of this invention to provide a hydraulic shockabsorbing device for vehicles in which a cooling device for suppressingthetemperature rise of the damping fluid is located at the lower part ofthe de-' vice while a suspension coil spring is provided around thedevice as the upper part thereof whereby a compact design of the deviceis afforded.

The nature, principle, utility, and further features of this inventionwill be apparent from the following detailed description with respect topreferred embodiments of the invention when read in conjunction with theaccompanying drawings, throughout which like parts are designated bylikereference numerals.

to this invention as applied to a motorcycle;

FIGS. 2 and 3 are side views, in longitudinal section, showing theessential parts of one example of the hy draulic shock-absorbing deviceaccording to this invention and respectively indicating (retraction) andascent (extension) of the piston and piston rod;

FIG. 4 is a side view, in longitudinal section with parts cut away,showing another embodiment of the invention, and

FIG. 5 is a similar view showing still another example of the deviceaccording to the invention.

DETAILED DESCRIPTION In the first example of the shock-absorbing deviceas illustrated in FIGS. 2 and 3, there is provided a cylinder 2filledwith a damping fluid and containing a piston l slidably fittedtherein. The cylinder 2 is supported concentrically withinan outercylinder or casing 3 and is provided at its upper and with a slidebearing 5 through which the piston rod 4 of the piston 1 is slidablypassed. The upper end of the outer casing 3 is provided with internalscrew threads for receiving the threaded part of a gland 6, which uponbeing tightened, presses downward on the upper surface of the slidebearing 5 and thereby fixes together the cylinder 2 and the outer casing3.

Theouter cylindrical surface of the cylinder 2 and I the innercylindrical surface of the outer casing3, being of different diametersand being mutually concentric,

form a cylindrical space therebetween, which is used as a fluid storagechamber 7. A cooling device 8 is provided at .the lower part of thisfluid storage chamber 7.

In the example illustrated in FIGS. 2 and 3, this cooling device 8 isanother cylinder formed integrally with the outer casing 3 and disposedconcentrically around the lower part thereof. This cooling device isprovided on its outer surface with cooling fins 28 for increased coolingeffect. The inner diameter of this cooling device 8 is greater than theouter diameter of the lower part of the outer casing 3, wherebya coolerchamber 8a is formed th erebetween, the lower part of the outer casing 3constituting a partition 9 between the fluid storage chamber 7 and thecooler chamber 8a.

Upper and lower through holes 10 and 10a are formed at spaced-apartpositions in the partition 9 and 'thereby constitute communicativepassageways beends on respectively opposite sides with respective valveswhereby some (12) of the holes are for the compression stroke (i.e.,retraction stroke) of the piston, while the other holes (13) are for thereturn stroke (i.e., the extension stroke) of the piston.

More specifically, the upper surface of the piston l is provided with anannular valve plate 14 for closing the passage hole 12 during theextension stroke, while the lower surface of the piston 1 is providedwith an annular valve plate for closing the passage hole 13 during theretraction stroke. These valve plates are fitted around the inner endpart of the piston rod 4 and can be separated away from theirrespective'piston surfaces with specific gap distances. The valve plate14 is stiff, while the valve plate 15 is flexible.

Within the cylinder 2 at the lower end thereof, there is fixedlyinstalled a valve seat 16 provided with through holes 17, 17, whichcommunicate at their lower ends with passage holes 18, 18 communicatingattheir ends with the lowest part of the aforedescribed I plate 21provided on the lower surface side of the first valve plate 19 are somounted with a hollow rivet 23 that the small holes 20 can be closed bythe second valve 21. This hollow rivet 23 has a central orifice 24, thelower open end of which communicates with the aforementioned passageholes l8, 18, thereby communicating with the lower end of the fluidstorage chamber 7.

Between the aforedescribed slide bearing 5 and the piston rod 4, thereis provided a clearance a for permitting passage of the fluid. A smallchamber 25 is formed between the slide bearing 5 and the gland 6 and iscommunicative with the upper end of the fluid storage chamber 7 throughan escape hole 26. Escape of fluid from the chamber 25, through thenecessary clearance between the piston rod 4 and the gland 6, to theoutside is prevented by an oil seal 29 disposed around the piston rod 4and in the upper part of the chamber 25.

Reference numeral 27-designates a suspension coil spring disposed aroundthe outer cylinder 3 and bearing at its lower end on a part of the outercylinder 3 by way of an annular spring retainer 40. As shown in FIG. 1,the upper end of this spring 27 is held down by a flanged member'35fixed to the upper end of the piston rod 4. The upper end of the rod 4is pivoted to. a chassis C of a motorcycle by means of a pivot pin 37and the lower end of the outer casing 3 is pivoted to a rear fork R. Thesuspension coil spring 27 supports the weight of the vehicle body andthe rider.

In another example of a hydraulic shock-absorbing device according tothis invention as illustrated in FIG. 4, the cooling device comprises acooler 8 disposed at one side of the lower part of the outer casing 3and the lower through hole 10a communicating the fluid storage chamber 7and the cooler 8 is divided into upper and lower passageways 10a, andIOain which check valves 30 and 31 are respectively installed withmutually reversed direction. Furthermore, a deflector 32 is installedwithin the cooler 8. In other respects, this example is similar to thepreceding example illustrated in FIGS. 2 and 3.

More specifically, of the two divided lower passageways 10a and l0a thehigher passageway 10a, is provided therewithin with a check valve 30permitting fluid flow only from the fluid storage chamber 7 to thecooler chamber 8a, while the lower passageway 10a is providedtherewithin with a check valve 31 permitting fluid frow only from thecooler chamber 8a to the fluid storage chamber 7. When the piston ldescends or retracts, the fluid flowing out from the lower chamber 2a ofthe cylinder 2 is caused to flow into the cooler chamber 8a only throughthe higher passageway 10:1,.

The above mentioned deflector 32 is of curved L shape in verticalsection as shown in FIG. 4, having a vertical part and a substantiallyhorizontal lower flange with an extreme edge 32a disposed at a heightintermediate between the two passageways 1011 and 10:1 This deflector 32thereby guides the fluid flowing into and out of the cooler chamber,thereby increasing the rate of cooling of the fluid.

The cooler 8 in the instant example is provided at its' top part with aopening for supplying fluid, which opening is normally closed with ascrew plug cover 33.

In still another example of this invention as illustrated in FIG. 5, acooler 38 of the cross-fin type, comprising a cooling tube 38a connectedat its ends to the upper and lower through holes 10 and 10acommunicating with the fluid storage chamber 7, and cross fins 37disposed parallelly to each other and substantially perpendicularly toone or more passes of the cooling tube 38a. Where a cooler of tubulartype is used as in this example, fluid pump (not shown) can be installedand operated to cause forced circulation of thefluid of the fluidstorage chamber 7 through the cooler. I

Except for the different features described above, the other features ofconstruction of the examples illustrated in FIGS. 4 and 5, are similarto those of the first example shown in FIGS. 2 and 3.

These examples of the shock-absorbing device ac cording to thisinvention operate in the following manner.

Referring first to FIGS. 2 and 3, when a load is applied on the device,that is, on the piston rod 4 to cause it to retract and move downward asviewed in the drawing, a portion of the damping fluid within the lowerchamber 2a of the cylinder 2 passes upward through the passage hole 12in the piston l and, pushing open the upper valve plate 14, flows intothe upper chamber 2b of the cylinder 2.

At the same time, the second valve plate 21 of the valve seat 16 opensthe small holes 20 of the first valve plate 19, and a portion of thefluid within the lower chamber 2a passes through the passage hole 17 andflows downward from the valve seat, simultaneously flowing out alsothrough the orifice 24. The fluid which has flowed thus out of thebottom of the cylinder 2 passes through the passage holes 18 and entersthe fluid storage chamber 7. a

This fluid flows at a high velocity through the lower through hole andinto the cooler chamber 8a and, mixing with the fluid at low temperaturewithin this chamber, is cooled.

Then, when the piston l completes its downward or retraction stroke andbegins its upward or extension stroke, the cooled fluid within thecooler chamber 811 flows through the lower through hole' 10a, enters thefluid storage chamber 7, passes through the passage holes 18 and passageholes 17, and, pushing open the first valve plate 19, enters the lowerchamber 2a of the cylinder 2. During this reverse flow of the fluid,reverse entering flow occurs also through the orifice 24.

At the same time, a portion of the fluid in the upper cylinder chamber2h passes downward through. the passage hole 13 and, pushing open thelower valve plate 15, flows into the lower cylinder chamber 2a.Simultaneously, another portion of the fluid in the upper cylinderchamber 2b passes upward through the clearance a between the slidebearing 5 at the upper part of the cylinder 2 and the piston rod 4,passes through the small chamber 25, flows through the escape hole 26into the fluid storage chamber 7, flows through the upper through holeinto the cooler chamber 8a, and is cooled by mixing with thelowtemperature fluid within the cooler chamber 8a.

When the fluid temperature rises further and the viscosity of the fluidbegins to decrease, the quantity of fluid flowing out through theclearance a between the slide bearing 5 and'the piston rod 4 increases,and the fluid flowing into the fluid storage chamber 7 reaches thecooler chamber 8a through the upper through hole 10 and, furthermore,flows through a circulatory path through the lower through hole 10a intothe lower part of the fluid storage chamber 7, through the passage holes18 and I7, and into the lower cylinder chamber 20. The fluid is therebycooled during this flow thereof.

In the example illustrated in FIG. 4, fluid which has flowed downwardfrom the upper part of the storage chamber 7 enters thecooler chamber 8athrough the 'upper through hole l o. Fluid from the lower part of thestorage chamber 7 passes through the higher hole 10a, of the throughholes, pushing open the check valve 30, and enters the cooler chamber8a. The fluid which has entered the cooler chamber Set is guided upwardby the deflector 32 and, after reaching the upper part of the chamber8a, flows downward on the opposite side of the deflector 32.

When the'piston'l ascends in its extension stroke, and fluid is drawninto the lower cylinder chamber 2a from the cooler chamber 8a, the fluidthus drawn pushes open the check valve 31 'ofthe lower through hole ,l0aand flows in the lower part of the fluid storage chamber 7. I r In thehydraulic shock-absorbing device'according to this invention asdescribed above, an outer cylinder or casing 3 is providedconcentrically around a cylinder 2 filled with a fluid and containingapiston l slidably fitted therein. Accordingly, a cylindrical fluidstorage chamber 7 is formed between the outer casing 3 and the cylinder2, and this chamber 7 is communicative with upper and-lower cylinderchambers 2b and 2a and also with the interior of a cooling device 8.

By this construction of the shock-absorbing device, the reciprocatingmovements of the piston 1 due to outside forces cause flow movements ofthe fluid within the cylinder 2 and the chamber 7, whereby the fluid isintroduced into and subsequently drawn out of the cooling device 8, andtemperature rise of the fluid is thereby suppressed. The viscosity ofthe fluid within the cylinder 2 is thereby prevented from decreasing,and impairment of the damping action of the device as shock-absorbingdevice is prevented. Therefore, an extremely comfortable shockabsorbingaction can: be obtained even when the vehicle is running over.unlevelcdground or rough terrain.

Furthermore, since there is practically no temperature rise, .there isno possibility of an abnormal rise in the pressures within the cylinder2 and the outer casing 3 to cause leakage of the fluid due to damagesuch as rupturing of seals.

From the foregoing, it has now been made clear that this inventionprovides a hydraulic shock-absorbing device which is compactin designbecause of the provi sion of the cooling device at the lower part of thede- 6 vice and of the suspension coil spring at the upper part of thedevice.

We claim:

I. In a hydraulic shock-absorbing device for use in vehicles having ahydraulic cylinder containing a damping fluid and receiving therein apiston which divides the interior of said hydraulic cylinder into upperand lower chambers, said piston being connected to a piston rod whichtransmits external axial forces to said pis ton, and an outer casingprovided concentrically with and exteriorly of said hydraulic cylinderto thus form a damping fluid'storage chamber having an upper and a lowerend, between the outside surface of said hydraulic cylinder and theinner surface of'said casing, said storage chamber communicating at itsends with respective outer extremities of said upper and lower chambersso that the damping fluid in said lower chamber flows into said upperchamber and into said lower end of said storage chamber during aretraction stroke of said piston, and the damping fluid in said upperchamber flows into said lower chamber and into the upper end of saidstorage chamber during an extension stroke. of said piston; theimprovement comprising:

a damping fluid cooling means disposed on said outer casing adjacent thelower portion of said storage chamber, said outer casing having upperand lower through holes formed therein and spaced apart along thedirection of the longitudinal axis of said hydraulic cylinder, saidthrough holes communicatively connecting said damping fluid coolingmeans with said storage chamber;

an annular member means disposed in said storage chamber so as to beinterposed between said hydraulic cylinder and said outer casing at aposition intermediate between said two through holes, said member meanspartitioning said storage chamber into upper and lower parts; and

a vehicle weight carrying suspension coil spring disposed around saidouter casing substantially above said cooling means, said improvementoperating whereby when said damping fluid is caused to flow into arespective one of said upper and lower parts of said storage chamber, itflows into the other part of said storage chamber through said lowerthrough hole, said damping fluid cooling means and said upperthroughhole, thus-executing forced circulatory motion inside saidshock-absorber to cause I continuous cooling of said damping fluid.

2. A- hydraulic shock-absorbing device as claimed in claim 1 in whichsaid cooling-means has cooling fins disposed thereon for dissipatingheat therefrom.

3. A hydraulic shock-absorbing device as claimed in 7 claim 1 in whichsaid cooling means has an annular cooling chamber disposed around thelower portion of said outer casing and communicating with said storagechamber by means of said two through holesv 4. A hydraulicshock-absorbing device as claimed in claim 1 in which said cooling meanscomprises a radiator-type cooling coil having extremities thereofconnected communieatively with said fluid storage chamber through saidupper and lower through-holes.

5. A hydraulic shock-absorbing device claimed in claim 1 in which saidcooling means comprises a cooler disposed on one side of the lowerportion of said outer casing, said cooler having cooling chamber whichcommunicates with said storage chamber by means of said two throughholes.

6. A hydraulic shock-absorbing device as claimed in claim 5, furthercomprising a third through hole formed in the lower portion of saidouter casing at a position intermediate between said two through holes,said annular member means being positioned intermediate between saidupper and said third through holes; first check valve means provided insaid third through hole and permitting fluid flow only from said lowerpart of said storage chamber to said cooling chamber; second check valvemeans provided in said lower through hole normally closed with a plugcover. l

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3795291Dated March 5, 1974 Inventor 8 Masaharu Naito, et a1 It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

[30] :Foreign Priority Document I Japanuo. 71770/1971 September 17, 1971In the drawings: Delete Fig. 6

Signed and sealed this I7th day of deptembe (SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents USCOMM-DC 60376-P69 FORM PO-IOSO (10-69) u.s. GOVERNMENTPRINTING OFFICE 1909 o-ase-aa-s.

1. In a hydraulic shock-absorbing device for use in vehicles having ahydraulic cylinder containing a damping fluid and receiving therein apiston which divides the interior of said hydraulic cylinder into upperand lower chambers, said piston being connected to a piston rod whichtransmits external axial forces to said piston, and an outer casingprovided concentrically with and exteriorly of said hydraulic cylinderto thus form a damping fluid storage chamber having an upper and a lowerend, between the outside surface of said hydraulic cylinder and theinner surface of said casing, said storage chamber communicating at itsends with respective outer extremities of said upper and lower chambersso that the damping fluid in said lower chamber flows into said upperchamber and into said lower end of said storage chamber during aretraction stroke of said piston, and the damping fluid in said upperchamber flows into said lower chamber and into the upper end of saidstorage chamber during an extension stroke of said piston; theimprovement comprising: a damping fluid cooling means disposed on saidouter casing adjacent the lower portion of said storage chamber, saidouter casing having upper and lower through holes formed therein andspaced apart along the direction of the longitudinal axis of saidhydraulic cylinder, said through holes communicatively connecting saiddamping fluid cooling means with said storage chamber; an annular membermeans disposed in said storage chamber so as to be interposed betweensaid hydraulic cylinder and said outer casing at a position intermedIatebetween said two through holes, said member means partitioning saidstorage chamber into upper and lower parts; and a vehicle weightcarrying suspension coil spring disposed around said outer casingsubstantially above said cooling means, said improvement operatingwhereby when said damping fluid is caused to flow into a respective oneof said upper and lower parts of said storage chamber, it flows into theother part of said storage chamber through said lower through hole, saiddamping fluid cooling means and said upper throughhole, thus executingforced circulatory motion inside said shock absorber to cause continuouscooling of said damping fluid.
 2. A hydraulic shock-absorbing device asclaimed in claim 1 in which said cooling means has cooling fins disposedthereon for dissipating heat therefrom.
 3. A hydraulic shock-absorbingdevice as claimed in claim 1 in which said cooling means has an annularcooling chamber disposed around the lower portion of said outer casingand communicating with said storage chamber by means of said two throughholes.
 4. A hydraulic shock-absorbing device as claimed in claim 1 inwhich said cooling means comprises a radiator-type cooling coil havingextremities thereof connected communicatively with said fluid storagechamber through said upper and lower through holes.
 5. A hydraulicshock-absorbing device as claimed in claim 1 in which said cooling meanscomprises a cooler disposed on one side of the lower portion of saidouter casing, said cooler having cooling chamber which communicates withsaid storage chamber by means of said two through holes.
 6. A hydraulicshock-absorbing device as claimed in claim 5, further comprising a thirdthrough hole formed in the lower portion of said outer casing at aposition intermediate between said two through holes, said annularmember means being positioned intermediate between said upper and saidthird through holes; first check valve means provided in said thirdthrough hole and permitting fluid flow only from said lower part of saidstorage chamber to said cooling chamber; second check valve meansprovided in said lower through hole and permitting fluid flow only fromsaid cooling chamber to said lower part of said storage chamber; and adeflecting member having an extreme edge disposed intermediate betweensaid lower and third through holes.
 7. A hydraulic shock-absorbingdevice as claimed in claim 5 in which said cooler has an opening at thetop thereof for supplying fluid thereto, said opening being normallyclosed with a plug cover.